← Back to Education · General GI

Tips for adequate bowel prep

Practical steps drawn from current US multi-society guidance

What “adequate” means

In current guidance, “adequate” means the colon is clean enough that the findings can be used to set the standard next screening or surveillance interval.

  • Adequate prep is a priority quality measure, with a target of 90% of exams.
  • Adequacy should be tracked for each endoscopist and for the unit as a whole.
  • The recommendations mainly apply to outpatients at low risk of poor prep. Higher-risk people may need a tailored plan.

Scoring prep quality with the BBPS

Boston Bowel Preparation Scale

The scale divides the colon into three segments: right, transverse, and left. Each segment gets a score from 0 to 3, and the three scores are added for a total from 0 to 9.

0Solid stool blocks the view, so the lining can’t be assessed.
1Only part of the lining is visible. Discoloration, leftover stool, or murky liquid hides the rest.
2The lining is seen well, with only slight discoloration or a few specks of stool or murky fluid.
3The whole segment is clearly seen, with no discoloration, debris, or murky liquid.

EvidenceA common adequacy rule: every segment scores at least 2. Because each segment must reach 2, the total is automatically at least 6.

Total-only cutoffs can let one poorly cleaned segment pass. A 2024 analysis also found more missed lesions at a total of 6 than at 7 to 9, so some units set a stricter bar.

Worked examples

Example A

Right 3, transverse 2, left 2. Total 7, and every segment is at least 2.

Adequate

Example B

Right 2, transverse 2, left 2. Total 6, and every segment is at least 2.

Adequate

Example C

Right 1, transverse 3, left 3. Total 7, but the right colon scores only 1. The total looks fine; the segment rule catches the problem.

Not adequate by the segment rule

Timing the split dose

Focused on morning procedures

  • For morning colonoscopies, split the prep: part the night before and part the morning of.
  • Start the second portion 4 to 6 hours before the procedure start.
  • Finish the prep at least 2 hours before the procedure start.
  • A same-day regimen can be an acceptable option for low-risk outpatients having afternoon procedures. For morning procedures, it is considered the weaker choice.

Worked example: for an 8:00 a.m. procedure, the second portion would begin between 2:00 and 4:00 a.m. and be finished by 6:00 a.m. at the latest.

Hours before the scheduled procedure start. Your team sets the actual times.

Diet and fluids

  • Limit diet changes to the day before the procedure.
  • On that day, the early and midday meals should be clear liquids or low-fiber, low-residue foods.
  • PracticalLow-residue examples include white bread or plain pasta, eggs, tender lean meat or fish, and well-cooked, peeled fruit or vegetables.
  • PracticalDuring the low-residue window, avoid seeds, nuts, popcorn, and raw vegetables or fruit with skins.
  • PracticalClear liquids include water, clear broth, pulp-free juice, clear sports drinks, and plain tea or black coffee. Avoid milk and alcohol.
  • PracticalAvoid red and purple liquids, which can be mistaken for blood during the exam.
  • PracticalUnless a clinician has limited fluids, sip clear liquids through the day to stay hydrated.
Clear water or broth
Allowed
Red or purple drink
Avoid: can look like blood on the lining

Clear liquids are fine. Red and purple ones can look like blood on the lining during the exam.

Medicines and health conditions

  • Choose the regimen based on medical history, medications, and any adequacy reported from earlier colonoscopies.
  • PracticalBring a full list of medicines and supplements to the planning visit.
  • PracticalIron supplements can darken stool and may need to be paused in the days before, per your team’s instructions.
  • PracticalPeople on insulin or other glucose-lowering medicines need a specific plan, because fasting and clear liquids can lower blood sugar.
  • PracticalSome medicines that slow gut movement, including certain diabetes and weight-loss drugs, can affect prep and sedation planning. Follow your team’s current guidance on holding them.
  • PracticalConstipation, opioid use, and a history of poor prep can all call for a different plan.
  • SafetyOral sodium phosphate products are generally avoided in people with significant kidney disease, heart failure, or electrolyte problems.

Regimen, add-ons, and instructions

  • For low-risk outpatients, no single bowel-prep agent is preferred over the others.
  • Low-volume regimens are emphasized.
  • Oral simethicone is suggested as an add-on, because it breaks up the bubbles and foam that can hide the lining. Other add-ons are not suggested for routine use.
  • Give both spoken and written instructions for every part of the prep. This is strongly recommended.
  • PracticalAsk the person to explain the schedule back in their own words.
  • PracticalPut the times on a calendar or phone reminder, and confirm the person has the correct product and enough toilet access.
  • PracticalIf sedation is planned, arrange a ride home.

During the exam

For endoscopy teams

  • Routine use of an irrigation pump during colonoscopy is suggested to help clear residue.
  • If the person reports poor prep, advance the scope to the sigmoid colon to check before deciding to stop.
  • Same-day salvage steps, such as extra cleansing during the procedure, can help when prep is inadequate.
  • ASGE and ESGE recommend repeating the exam within one year after an inadequate prep.
  • PracticalRecord the BBPS score for each segment so adequacy can be tracked.

Quick checklist for the day before

  • ☐ Clear liquids or low-residue food only, as planned
  • ☐ First portion of the prep taken at the scheduled evening time
  • ☐ Written and spoken instructions reviewed
  • ☐ Medicines reviewed, including any planned pauses
  • ☐ Ride arranged if sedation is planned
  • ☐ Alarm set for the second portion

Contact your team right away if:

  • You can’t keep clear liquids down, or vomiting continues.
  • You feel dizzy or faint, become confused, or are passing very little urine.
  • You have severe belly pain or swelling, or a fever.
  • You can’t finish the prep on the planned schedule.

Key takeaways

  • Adequate prep has a defined standard. A common rule is that every BBPS segment scores at least 2.
  • For morning procedures, split the prep and finish at least 2 hours before the start.
  • Keep diet changes to the day before, and give both spoken and written instructions.
  • Consider a simethicone add-on, use an irrigation pump during the exam, and check the view before deciding to stop.

Sources and notes

  • US Multi-Society Task Force on Colorectal Cancer (ACG, AGA, ASGE), Optimizing Bowel Preparation Quality for Colonoscopy, published March 2025 in Gastroenterology and the societies’ journals. Read the Guideline Central summary and the joint press release.
  • Overview of the 2025 changes: Guideline Central. Trade coverage: Healio.
  • Lai EJ, et al. The Boston Bowel Preparation Scale: a valid and reliable instrument for colonoscopy-oriented research. Gastrointest Endosc. 2009;69(3 Pt 2):620–625.
  • Clark BT, et al. Quantification of adequate bowel preparation for screening or surveillance colonoscopy in men. Gastroenterology. 2016. Abstract on PubMed Central.
  • Scientific Reports, 2024: Boston bowel preparation scale score 6 has more missed lesions compared with 7–9. Full text on PubMed Central.

It is educational, not medical advice, and it does not replace the full guideline, the treating team’s instructions, or your unit’s protocol. Check the full guideline text before using any detail clinically.